hermes-agent/website/docs/developer-guide/desktop-plugin-sdk.md

---
sidebar_label: "Desktop Plugin SDK"
title: "Desktop Plugin SDK (@hermes/plugin-sdk)"
description: "Extend the native Hermes Desktop app — panes, pages, sidebar nav, status bar, palette commands, keybinds, themes, and a scoped backend namespace, with one import and no build step."
---

# Desktop Plugin SDK

The native [Hermes Desktop](../user-guide/desktop.md) app is contribution-driven: every
surface in the window — panes, routes, sidebar nav, status-bar items, palette
entries, keybinds, themes — registers into one central registry. Core registers
its surfaces exactly the way a plugin does, so the plugin story is the real one,
not a bolted-on afterthought.

A **desktop plugin** is a single ESM file that default-exports a `HermesPlugin`.
It imports one module — `@hermes/plugin-sdk` — and gets everything: the app's
live state, the gateway JSON-RPC door, a scoped REST/socket backend namespace,
React Query, and the app's own UI kit so plugin UI looks native by default. No
repo clone, no `npm run build`, no patching app source. Drop the file in
`$HERMES_HOME/desktop-plugins/<id>/plugin.js` and the app loads it within seconds
and hot-reloads every save.

:::warning This is not the web-dashboard plugin SDK
"Plugin" means several unrelated things across Hermes. This page is the **native
desktop app** (`hermes desktop`) SDK — the `@hermes/plugin-sdk` module and
`$HERMES_HOME/desktop-plugins/`. The **web dashboard** (`hermes dashboard`) has
its own, unrelated plugin system on `window.__HERMES_PLUGIN_SDK__` with a
`manifest.json` — documented at
[Extending the Dashboard](../user-guide/features/extending-the-dashboard.md). Python
CLI/gateway plugins are documented at [Build a Hermes Plugin](./plugins/index.md).
The three do not share code, APIs, or delivery. Only the backend `plugin_api.py`
namespace (`/api/plugins/<id>`) is shared between the desktop and dashboard SDKs.
:::

## Mental model

The SDK follows the VS Code module model. A plugin author imports exactly one
module and never touches app internals (they are lint-fenced out of a bundled
plugin, and fail to resolve in a disk plugin). Capability comes in tiers:

- **`host.state.*`** — readonly views over the app's live state (nanostore
  atoms): active session, per-session turn-busy, cwd, gateway socket status,
  model, profile, viewport. `gateway` is the WebSocket, not turn-busy.
- **`host.*` actions** — curated safe verbs: toast, navigate, tail logs,
  restart the gateway, subscribe to the gateway event stream.
- **`host.request`** — the gateway JSON-RPC door: sessions, config, skills,
  cron — everything the app itself calls.
- **`captureGatewayFileDownload()`** — capture a gateway file-save action
  immediately before starting a REST read, and retain it alongside the returned
  data. The action `(storedPath, suggestedName) => Promise<void>` keeps that
  read's connection/profile scope even if the user switches hosts before
  clicking. Invoke only on an explicit user download gesture, using the
  backend's persisted file path, never a guessed workspace path. Electron handles
  authenticated streaming, the native save dialog, and older-gateway fallback;
  plugins never receive credentials or open remote paths with `file://`. The
  host shows the same "Saved" / "Download failed" toasts as the Files panel and
  stays quiet on cancel; the promise settles when the save does and never
  rejects.
- **`ctx.rest` / `ctx.socket`** — your plugin's own backend namespace
  (`/api/plugins/<id>`) if you ship a `plugin_api.py`.
- **`ui.*`** — the design language: the app's real components, theme variables,
  icons, and formatters, so your UI matches the app pixel-for-pixel.

## Two delivery modes

| Mode | Where | Who | Build step |
|------|-------|-----|------------|
| **Disk** (recommended) | `$HERMES_HOME/desktop-plugins/<id>/plugin.js` | users, agents | none — plain ESM, loaded uncompiled |
| **Unified package** | `$HERMES_HOME/plugins/<id>/desktop/plugin.js` | plugins that also ship agent-side code | none — same disk pipeline |
| **Bundled** | `apps/desktop/src/plugins/<id>/plugin.tsx` | in-tree, shipped with the app | the app's own Vite build |

All three take the same `HermesPlugin` contract, appear in **Capabilities → Plugins**,
and enable/disable live. A unified package is just the disk door scanning inside
your agent plugin's folder — see
[One package, both SDKs](#one-package-both-sdks). Everything on this page is
written against the disk door (what you and the agent write);
[Bundled plugins](#bundled-plugins) notes the two
differences. Radio ships as a bundled SDK-only plugin, off by default. Enable it
in **Capabilities → Plugins** for free live streams, station search, and status-bar
playback controls with an audio-reactive waveform. It uses the existing plugin
toggle and contributes nothing while disabled. Reference demos live in the companion
[`hermes-example-plugins`](https://github.com/NousResearch/hermes-example-plugins)
repo.

## Quick start — your first plugin

Create `$HERMES_HOME/desktop-plugins/hello/plugin.js` (that's `~/.hermes/...`
by default). Desktop plugins are app-level — one root for every profile, gateway,
or remote machine the window connects to. The folder name must equal the plugin `id`.

```javascript
// ~/.hermes/desktop-plugins/hello/plugin.js
import { host, haptic, useValue } from '@hermes/plugin-sdk'
import { jsx, jsxs } from 'react/jsx-runtime'

function HelloPane() {
  const gateway = useValue(host.state.gateway)

  return jsxs('div', {
    className: 'flex h-full flex-col gap-2 p-3 text-sm',
    children: [
      jsx('div', { className: 'font-medium', children: 'Hello, Hermes' }),
      jsx('div', {
        className: 'text-(--ui-text-tertiary)',
        children: `gateway: ${gateway}`
      })
    ]
  })
}

export default {
  id: 'hello', // must match the folder name
  name: 'Hello',
  register(ctx) {
    ctx.register({
      id: 'pane',
      area: 'panes',
      title: 'hello',
      data: { placement: 'right', width: '260px' },
      render: () => jsx(HelloPane, {})
    })
    ctx.register({
      id: 'chip',
      area: 'statusBar.right',
      order: 130,
      render: () =>
        jsx('button', {
          type: 'button',
          className: 'px-1.5 text-[0.6875rem] text-(--ui-text-tertiary)',
          onClick: () => {
            haptic('tap')
            host.notify({ kind: 'info', message: 'Hello from my plugin!' })
          },
          children: 'hello'
        })
    })
  }
}
```

Save it. The app watches `desktop-plugins/`, loads the file within a few seconds,
and hot-reloads every later save in place. If it doesn't appear, run ⌘K →
**Reload desktop plugins**. If loading fails, a toast names the error — fix and
save again.

:::note No JSX, no build
The disk file is loaded **uncompiled**, so JSX syntax will not parse. Write UI
with `jsx()` / `jsxs()` calls from `react/jsx-runtime` (or `React.createElement`).
The only importable specifiers are `@hermes/plugin-sdk`, `react`, and
`react/jsx-runtime` — everything else fails to resolve, on purpose.
:::

## The plugin contract

A plugin default-exports a `HermesPlugin`:

```ts
interface HermesPlugin {
  /** Stable slug — becomes the `plugin:<id>` source and the id namespace. */
  id: string
  /** Human name for Settings / about UI. Defaults to `id`. */
  name?: string
  /** Registers on load when the user hasn't chosen (default true). Set false
   *  for opt-in plugins: they inventory in Capabilities ▸ Plugins, off until the
   *  user flips the switch. */
  defaultEnabled?: boolean
  /** Called once at load; wire contributions through `ctx`. */
  register: (ctx: PluginContext) => void
}
```

`register` receives a **scoped** `PluginContext`. It never touches the registry
directly — the context auto-tags provenance (`source: 'plugin:<id>'`) and
namespaces every contribution id (`<id>:<localId>`), so two plugins can never
collide.

```ts
interface PluginContext {
  /** Resolved source tag, e.g. `'plugin:hello'`. */
  readonly source: string
  /** Register one contribution (id namespaced, source stamped). Returns a disposer. */
  register: (c: PluginContribution) => () => void
  /** Register several at once; the returned disposer removes all of them. */
  registerMany: (cs: PluginContribution[]) => () => void
  /** REST to this plugin's own backend namespace (`/api/plugins/<id>`). */
  rest: <T>(path: string, opts?: PluginRestOptions) => Promise<T>
  /** Live WebSocket to this plugin's own namespace. Returns a disposer. */
  socket: (path: string, onMessage: (data: unknown) => void) => () => void
  /** Gateway event stream by type (`'*'` = all). Tracked: removed on unload/reload/disable. */
  onEvent: (type: string, listener: (event: GatewayEvent) => void) => () => void
  /** Any other cleanup to run on unload/reload/disable (store subscriptions, injected DOM). */
  onDispose: (fn: () => void) => void
  /** Scoped timers and DOM listeners — cleared with the plugin. Each returns a disposer. */
  setTimeout: (fn: () => void, ms: number) => () => void
  setInterval: (fn: () => void, ms: number) => () => void
  addEventListener: (target: EventTarget, type: string, listener: EventListener, options?: AddEventListenerOptions | boolean) => () => void
  /** The curated OS door: native notification, open-external, reveal-in-file-manager, clipboard. */
  os: PluginOs
  /** Plugin-scoped JSON persistence (keys live under `hermes.plugin.<id>.`). */
  storage: PluginStorage
}
```

A **contribution** is the one primitive every surface shares:

```ts
interface Contribution {
  id: string          // you write the local id; the host namespaces it
  area: string        // WHERE it goes (a contribution-area constant)
  title?: string
  order?: number      // sort within the area (lower = earlier)
  when?: () => boolean // dynamic visibility; re-evaluated by the area
  enabled?: boolean
  render?: () => ReactNode  // the component to mount
  data?: unknown      // area-specific payload (see the cookbook)
}
```

You provide `render`, `data`, or both, depending on the area.

## Contribution areas — the cookbook

Import the area constants from the SDK; each area has its own `data` payload.

| Surface | `area` | You provide |
|---------|--------|-------------|
| Layout pane | `PANES_AREA` (`'panes'`) | `title` + `render` + `data: { placement, dock?, width?, height? }` |
| Full page | `ROUTES_AREA` | `data: { path }` + `render` |
| Sidebar nav | `SIDEBAR_NAV_AREA` | `data: { path, label, codicon }` |
| Status bar | `STATUSBAR_AREAS.left` / `.right` | `render` (or `data` as `StatusbarItem`) |
| Title bar | `TITLEBAR_AREAS.left` / `.center` / `.right` | `data` as `TitlebarTool`, or a mount-scoped `<Contribute>` |
| Page header | `WORKSPACE_PAGE_HEADER_AREA` | `render` via a mount-scoped `<Contribute>` inside your page |
| ⌘K palette | `PALETTE_AREA` | `data: PaletteContribution` |
| Keybind | `KEYBINDS_AREA` | `data: KeybindContribution` |
| Theme | `THEMES_AREA` | `data` as a `DesktopTheme` |
| Composer | `COMPOSER_AREAS.*` | render slots, or middleware / attachment providers |
| Appearance settings | `APPEARANCE_AREAS.extra` | `render` — controls appended to Settings → Appearance |

### Panes

A pane is a tile in the layout tree. `placement` is the semantic role — the pane
stacks (as tabs) with existing panes of that role; the user can drag it anywhere
afterward.

```javascript
ctx.register({
  id: 'pane',
  area: 'panes',
  title: 'my pane',
  data: { placement: 'right', width: '260px' },
  render: () => jsx(MyPane, {})
})
```

`placement` is `'main' | 'left' | 'right' | 'top' | 'bottom'`. To land on a
specific **edge** instead of stacking, add a `dock` gesture — the same thing as
dragging onto a pane's drop chip:

```javascript
// Below the conversation, 200px tall.
data: {
  placement: 'bottom',
  dock: { pane: 'workspace', pos: 'bottom' },
  height: '200px'
}
```

`dock.pane` is any pane id (`workspace` is the main thread; also `sessions`,
`terminal`, `files`, `review`, `logs`); `dock.pos` is
`'top' | 'bottom' | 'left' | 'right' | 'center'`. Declare a `width`/`height` so
the pane doesn't claim half the zone.

Closing the only pane contributed by a plugin disables that plugin, which can
be re-enabled from **Capabilities → Plugins**. When a plugin contributes multiple
panes, closing one dismisses only that pane and leaves the plugin's other panes,
commands, and middleware active. **Reset layout** restores dismissed contributed
panes.

### Pages and sidebar nav

A route mounts a full page in the workspace pane, like any built-in view. Pair it
with a sidebar nav row (and/or a palette command) to make it reachable.

```javascript
import { ROUTES_AREA, SIDEBAR_NAV_AREA } from '@hermes/plugin-sdk'

ctx.registerMany([
  {
    id: 'page',
    area: ROUTES_AREA,
    data: { path: '/my-page' },
    render: () => jsx(MyPage, {})
  },
  {
    id: 'nav',
    area: SIDEBAR_NAV_AREA,
    data: { path: '/my-page', label: 'My Page', codicon: 'project' }
  }
])
```

`codicon` is a [VS Code codicon](https://microsoft.github.io/vscode-codicons/dist/codicon.html)
id. Navigate to a route from anywhere with `host.navigate('/my-page')`.

### Status bar and title bar

Status-bar items render into the left or right cluster of the bottom bar.
Simplest is a `render` function; for a plain button use `data` as a
`StatusbarItem` (`{ id, label?, icon?, detail?, variant?, menuItems?, … }`).

```javascript
import { STATUSBAR_AREAS, TITLEBAR_AREAS } from '@hermes/plugin-sdk'

ctx.register({
  id: 'count',
  area: STATUSBAR_AREAS.right,
  order: 120,
  render: () => jsx(MyStatus, {})
})
```

Title-bar tools live in `TITLEBAR_AREAS.left | .center | .right` as `TitlebarTool`
data (`{ id, label, icon, active?, onSelect? }`).

Title-bar slots are **permanent mount points**: a component you register there
stays mounted while the user moves between the chat and full pages (Capabilities,
Messaging, Artifacts, contributed routes), so a `useEffect` that injects global
side effects (a `<style>` tag, `html[data-*]` attributes, a `MutationObserver`)
runs its setup once per registration and its cleanup once at dispose — never
mid-navigation.

Controls that belong to ONE page (the Kanban board switcher) go in
`WORKSPACE_PAGE_HEADER_AREA` instead: it renders in the workspace panel's
tab-header row while that page is on screen and is empty otherwise. Register it
with a mount-scoped `<Contribute>` (below) so it leaves with the page.

### Palette commands and keybinds

```javascript
import { PALETTE_AREA, KEYBINDS_AREA } from '@hermes/plugin-sdk'

ctx.registerMany([
  {
    id: 'open',
    area: PALETTE_AREA,
    data: {
      id: 'my-page.open',
      label: 'Open My Page',
      keywords: ['my', 'page'],
      run: () => host.navigate('/my-page')
    }
  },
  {
    id: 'refresh',
    area: KEYBINDS_AREA,
    data: {
      id: 'my-page.refresh',
      label: 'Refresh My Page',
      category: 'My Plugin',
      defaults: ['mod+shift+r'],
      run: () => void doRefresh()
    }
  }
])
```

Keybinds are user-rebindable in settings; `defaults` is just the initial binding.

### Themes

A theme contribution ships a full `DesktopTheme` as its `data` (name, label,
colors, …). It appears in the theme picker like a built-in.

```javascript
import { THEMES_AREA } from '@hermes/plugin-sdk'

ctx.register({ id: 'noir', area: THEMES_AREA, data: myDesktopTheme })
```

Registering a theme lists it; it does not select it. `useTheme()` reads the
painted appearance (`theme`, `themeName`, `availableThemes`, `resolvedMode`) and
changes it (`setTheme`, `setMode`, `previewTheme`) from a component:

```javascript
import { Button, useTheme } from '@hermes/plugin-sdk'

function ThemePicker() {
  const { availableThemes, setTheme, themeName } = useTheme()

  return availableThemes.map(t => (
    <Button key={t.name} disabled={t.name === themeName} onClick={() => setTheme(t.name)}>
      {t.label}
    </Button>
  ))
}
```

A switch driven by something other than a render — a gateway connecting, a
socket event, any `host.onEvent` callback — has no component to hang the hook
on. Use `requestTheme(name)` there. An unresolvable name is refused rather than
coerced to the default skin, so the return value doubles as the availability
check and a wrong name can never silently reset someone's appearance:

```javascript
import { host, requestTheme } from '@hermes/plugin-sdk'

host.onEvent('gateway.ready', () => {
  if (!requestTheme('noir')) {
    host.notifyError('Connected, but the noir theme is not installed.')
  }
})
```

Both doors persist per profile, so a plugin-driven switch sticks exactly like a
manual pick. To tint the *active* theme rather than replace it, use
`setAccentOverride(hex)` and clear it in `ctx.onDispose` — the standalone
[Accent Picker](https://github.com/NousResearch/hermes-desktop-accent-picker)
plugin is the worked example (it is also a complete, installable disk plugin).

### Composer extensions

`COMPOSER_AREAS` (`top`, `bottom`, `underside`, `leading`, `actions`,
`attachments`, `middleware`) let a plugin add controls around the message
composer, provide an attachment source, or transform a draft before it is sent
(`ComposerMiddleware` with a `handler(draft) => draft | null`). `top` is a
banner strip above the input and `bottom` a row below the input grid, both
inside the composer chrome; `underside` is the floating strip BELOW the whole
composer with no chrome of its own — the seat for a suggestion pill or a status
hint that should sit outside the input frame (the next-prompt plugin renders its
"next prompt" pill there).

### Composer draft API — read and write the live input

For everything the composer areas can't do — put text INTO the input, replace
what's there, read the current draft, or send it — use `host.composer`. This
is the supported door; reaching for the ProseMirror DOM, `[data-composer-target]`
lookups, or synthetic `InputEvent`s is out of the plugin surface (catalog rule 8)
and breaks the moment the app's markup moves. Addressing: `null` = the composer
the user is typing in; a session id (stored or runtime) = that session's
composer, in the primary pane or a tile; `'new'` = the fresh draft that has no
session id yet.

```javascript
import { host } from '@hermes/plugin-sdk'

// Append to the active composer (modes: 'block' | 'inline' | 'prefix';
// 'prefix' seats a slash command at the start). Acknowledged like setDraft:
// true when a mounted surface applied the text, false when the text is blank
// or no live surface answers for the address.
const inserted = await host.composer.insertText(null, 'draft note', { mode: 'inline' })

// Replace a session's whole draft — '@'-ref and '/command' tokens hydrate
// into chips exactly like an official paste. False when no mounted surface
// answers (an unmounted session is never half-written).
const ok = await host.composer.setDraft('sess-1', 'plan:\n- @file:src/app.ts')

// Read the live draft: the mounted surface's in-DOM text (unsaved keystrokes
// included), falling back to the debounced persisted stash. Null when nothing
// holds it.
const text = await host.composer.getDraft('sess-1')

// Send as if the user typed + pressed Enter. Fail-closed like the app's own
// panels: no visible surface for the address → false, never a broadcast.
const sent = host.composer.submit('sess-1', 'ship it')

// Put the caret in a composer (same addressing). insertText/setDraft already
// focus a visible surface they paint; use this to return the caret after a
// plugin popover closes or from a "go to input" keybind.
host.composer.focus(null)
```

```ts
host.composer: {
  getDraft(sessionId: string | null): Promise<string | null>
  setDraft(sessionId: string | null, text: string): Promise<boolean>
  insertText(sessionId: string | null, text: string, opts?: { mode?: 'block' | 'inline' | 'prefix' }): Promise<boolean>
  submit(sessionId: string | null, text: string): boolean
  focus(sessionId: string | null): void
}
```

**Arbitration.** Every verb is fail-closed on its address: a request is
answered only by the mounted composer that owns that session (its tile, or the
primary pane when it shows that session); `null` is answered only by the surface
the app's focus bus currently routes to; `'new'` only by the primary pane while it
shows no session — it never falls through to the active composer. No exact
surface → `null`/`false`, never
a broadcast into whichever pane happens to be mounted. Writes go through the
app's own paint path, so `@`-ref / `/`-command tokens hydrate as chips and the
result is byte-for-byte what the user would get by pasting. These are discrete,
user-triggered actions with the same authority as typing — no plugin "owns" the
draft afterwards, so there is **nothing to tear down** on disable; a plugin that
wants a persistent presence around the input uses a `COMPOSER_AREAS` slot instead.

A multi-session plugin keeps its per-session state on its side (which session
its panel is editing) and passes that id here; the bus guarantees one
plugin write can never land in another session's composer.

**Migrating off DOM reach-in** (the held catalog plugins that motivated this API):

| Plugin | Was | Now |
|---|---|---|
| next-prompt (#120660) | `window.dispatchEvent(new CustomEvent('hermes:composer-insert', …))` + a `setTimeout` `hermes:composer-focus`; `[data-composer-target]`/`[data-pane-hidden]` scan for the visible target | `await host.composer.insertText(null, suggestion.text, { mode: 'block' })`, then `host.composer.focus(null)` if the pill lost the caret |
| prompt-snippets (#116030) | same `hermes:composer-insert` event; `[data-slot="composer-input"]`/ProseMirror `textContent` + synthetic `InputEvent` fallback; `surfaceEditorEl().focus()` | `host.composer.insertText(sid, text, { mode: 'block' })`; `setDraft(sid, (await getDraft(sid) ?? '') + '\n' + text)` replaces the fallback; `host.composer.focus(sid)` — `sid = host.state.focusedSessionId.get()` |
| prompt-enhancer (#116031) | walks the editor's child nodes to serialize, rebuilds chip DOM, `replaceChildren` + synthetic `InputEvent` | `const draft = await host.composer.getDraft(sid)` → transform → `await host.composer.setDraft(sid, enhanced)` (chips hydrate app-side); revert is another `setDraft` |
| memory-review (#115966) | `host.request('slash.exec', { session_id, command })` for `/memory …` — already SDK-only | optional: `host.composer.insertText(sid, '/memory pending', { mode: 'prefix' })` to seat the command for the user instead of executing it |
| intelligent-tool-break (#115964) | "Message" button only toasts "type /break" (no composer write) | `host.composer.setDraft(host.state.focusedSessionId.get(), '/break ')` then `host.composer.focus(null)` restores the intended behaviour |

`sessionId` in the table is the id the plugin's UI is bound to; for a composer
slot render it is `host.state.focusedSessionId.get()`.

### Session rows — decorations + the session list API

`SESSION_ROW_AREAS` (`leading`, `trailing`) let a plugin decorate sidebar
session rows. Register a `data` contribution whose `render({ sessionId })`
returns a small element (a badge, a swatch, a tag) or `null` for rows you don't
own — registering costs nothing on every other row:

```ts
import { SESSION_ROW_AREAS, type SessionRowSlotContribution } from '@hermes/plugin-sdk'

ctx.register({
  area: SESSION_ROW_AREAS.trailing,
  id: 'my-tag',
  data: {
    render: ({ sessionId }) => (owned.has(sessionId) ? <span className="my-tag">★</span> : null)
  } satisfies SessionRowSlotContribution
})
```

Pair it with the session list API, which writes the same stores the app's own
controls write (so a plugin action and a hand click can never disagree):

```ts
host.sessions.pin(storedSessionId: string, pinned?: boolean, index?: number): void
host.sessions.reorder(storedSessionIds: string[]): void   // Recents; [] = clear manual order → default sort
host.sessions.reorderPinned(storedSessionIds: string[]): void  // Pinned section; omitted pins keep their slot
host.sessions.setColor(storedSessionId: string, color: string | null): void
```

Ids are STORED session ids: a live id is resolved to its durable lineage root,
so pins and colours survive compression's id rotation — and the row-decoration
slots hand your render that same durable id (`_lineage_root_id ?? id`), never
the live one. Resolution goes through the rows this window has loaded; an id
that matches no loaded row is written as given, so pass the slot's durable id
(not a live id you remembered) for a session that may have scrolled out of the
list. `reorder` accepts the same ids and maps each to its row's live id
internally — the Recents order store is keyed by the live id, like the drag
path. `pin(id, true, index)` slots the pin at that position in the
Pinned list (a drop target between two pins); without `index` it appends, like
the row's ⇧-click.

**Arbitration.** The verbs are discrete user-triggered edits of user data —
last write wins, exactly as if the user had clicked, and no plugin owns the
result afterwards. Slot contributions are ALL mounted (registration order, not
first-wins), each inside its own error boundary: a plugin that throws or
returns `null` for a row cannot suppress another plugin's decoration on it, and
two decorations on one row render side by side. Core keeps the row's layout,
gestures and title — slots augment, never replace.

**Teardown.** The verbs need none. Slot contributions are removed by the
`ctx.register` disposer (disable/reload drops them and the row re-renders
without the decoration).

Migration for the held catalog plugins:

- **drag-to-pin-session** — replace the `__reactFiber$*` walk for `onTogglePin`
  / `onReorderSessions` / `session._lineage_root_id` with the row's slot id
  (`render: ({ sessionId }) => …` under `SESSION_ROW_AREAS.leading` gives you
  the durable id per row), then `host.sessions.pin(sessionId, true, dropIndex)`
  for a drop into the Pinned section, `host.sessions.pin(sessionId, false)` for
  a drop back into Recents, `host.sessions.reorderPinned(ids)` for a drag
  within the Pinned section, and `host.sessions.reorder([])` for its
  "reset manual order" path.
- **better-session-appearance** — replace the `localStorage`
  `hermes.desktop.sessionColors` write and the fiber-harvested `onChange` with
  `host.sessions.setColor(sessionId, hex)` (`null` clears), and render its
  per-row glyph through `SESSION_ROW_AREAS.leading` instead of mutating the
  row's status dot (the durable id it needed from `_lineage_root_id` is the
  slot's `sessionId`).

`COMPOSER_AREAS.modelPill` overrides the model pill's **label** — a provider
(`{ label: (ctx: ComposerModelPillContext) => string | null }`) receives
`{ model, reasoningEffort, compact }` and returns the text to show, or `null` to
let the next provider (then the core label) win. The pill keeps its chrome, pin
dot, and menu; only the label changes — the sanctioned replacement for the
MutationObserver text-rewriting plugins do today.

#### Model pill label providers

```ts
import { COMPOSER_AREAS, type ComposerModelPillContext, type ComposerModelPillProvider } from '@hermes/plugin-sdk'

interface ComposerModelPillContext {
  model: string            // the model slug the pill would show
  reasoningEffort: string  // the session's live effort level, '' when the model has none
  compact: boolean         // floating-composer mode: chevron only, providers are NOT consulted
}
interface ComposerModelPillProvider {
  label: (ctx: ComposerModelPillContext) => string | null
}

ctx.register({
  area: COMPOSER_AREAS.modelPill,
  id: 'my-label',
  data: { label: ({ model, reasoningEffort }) => reasoningEffort ? `${model} · ${reasoningEffort}` : null } satisfies ComposerModelPillProvider
})
```

**Arbitration.** Providers are consulted in registry order and the *first
non-empty string wins*; later providers are not called. Anything else declines
and the next provider is asked: `null`, `''`, a whitespace-only string, and any
non-string value (an object, array or number is never rendered — the label is
placed straight into JSX). A provider that **throws** also declines — the error
is swallowed and the pill falls through to the next provider, then to the core
label, so a broken plugin can never blank the pill. `reasoningEffort` is always
a `string` (`''` when the model has no effort level, never `undefined`). In
compact (floating) mode the pill renders only the chevron and no provider is
called. `label()` is re-evaluated only when the registry, the model, the effort
level or the compact flag changes.

**Teardown.** The provider is an ordinary data contribution: `ctx.register`
returns its disposer and the loader drops it when the plugin is disabled or
reloaded, at which point the core label is restored. There is nothing to undo
in `ctx.onDispose`.

**Migrating compact-reasoning-label.** The plugin used to find the pill via
`[data-slot="composer-root"] button span.truncate`, regex-strip a trailing
effort word from `span.textContent`, and re-run that sweep from a body-wide
`MutationObserver` plus a 1 s `setInterval`. On current builds the core label no
longer contains the effort word (the level has its own `ReasoningPill`), so the
strip is a no-op; the sanctioned shape is to compute the label from the context
instead of editing rendered text:

```js
register(ctx) {
  ctx.register({
    area: COMPOSER_AREAS.modelPill,
    id: 'compact-reasoning-label',
    // Decline (null) whenever there is nothing to change so the core label wins.
    data: { label: ({ model }) => shorten(model) ?? null }
  })
  // No MutationObserver, no setInterval, no injected <style>: the contribution is
  // disposed with the plugin.
}
```

The reasoning-pill visibility CSS the plugin also injected has no hook; it is
only needed if the app ever hides that label at narrow widths.

### Appearance settings

`APPEARANCE_AREAS.extra` renders contributions at the end of **Settings →
Appearance**, after the built-in sections. It is the seam for a plugin that
used to inject nodes into that page or drive its widgets through React
internals.

```ts
APPEARANCE_AREAS = { extra: 'appearance.extra' } as const

ctx.register({
  area: APPEARANCE_AREAS.extra,
  id: 'session-colour-rules',          // unique within your plugin
  render: () => <MyAppearanceCard />   // any React tree; SDK hooks allowed
})
```

*Arbitration:* every registration mounts, in registry order, each inside its
own error boundary — a contribution that throws collapses to an inline error
card naming its `id` (with Retry) and the rest of the page (and other plugins'
cards) keep rendering. The slot mounts on the top-level Appearance page only,
not on deep-link subpages (`settings/appearance/<section>`), and there is no
"first wins" — plugins cannot suppress each other here.

*Teardown:* the registration is owned by the plugin loader; disabling or
reloading the plugin disposes it and the card disappears on the next render.
Nothing persists app-side, so there is nothing to clean up in `ctx.onDispose`.

For colour picking use the app's own swatch grid — `ColorSwatches` (already an
SDK export) renders exactly what the profile rail and project dialog render,
with your own `onChange`; feed it `PROFILE_SWATCHES` and pair it with
`host.sessions.setColor(id, color)` for session colours.

Migrations for the plugins that motivated this slot:

* **better-session-appearance** — replace the fiber walk that harvests the
  Appearance submenu's `{ onChange, swatches }` and the `clearBtn.after(...)` /
  `host.appendChild(panel)` injection into the app dropdown with one
  `ctx.register({ area: APPEARANCE_AREAS.extra, id: 'rules', render })` whose
  card renders `<ColorSwatches swatches={PROFILE_SWATCHES} value onChange />`
  plus its bold/glyph/auto-rule controls; drop the `data-better-session-appearance`
  attribute writes and the dropdown `max-height` overrides.
* **hermes-appearance-hub** — mount its paper-texture / font / intro-copy
  controls as an `APPEARANCE_AREAS.extra` card instead of a status-bar menu
  that reaches into Settings; the settings *values* still go through
  `host.settings` (allowlisted keys) and `THEMES_AREA`.

### Embedding external content

Use the SDK's `<SandboxedFrame src title />` for any external web content
(reader views, dashboards, docs). It renders a sandboxed iframe with the app's
guest-content posture: opaque origin, `allow-scripts` by default, `no-referrer`,
lazy loading. Never mount a raw Electron `<webview>`: it lands on the app's
`persist:` preview partition, sharing the app's cookies and storage.

```ts
interface SandboxedFrameProps {
  src: string      // absolute http(s): or data: URL; any other scheme renders nothing (console.warn)
  title: string    // required — an untitled frame is unlabelled in the a11y tree
  sandbox?: string // extra tokens; filtered through the allowlist below
  className?: string; style?: CSSProperties
  onLoad?, onError?: ReactEventHandler<HTMLIFrameElement>
  ref?: Ref<HTMLIFrameElement>
}
```

The props are an explicit allowlist, not `ComponentProps<'iframe'>`: `allow`
(Permissions-Policy delegation — would hand a third-party site the mic/camera
grant the app holds), `srcdoc`, `name`, `allowFullScreen`, `csp`,
`credentialless` and every other iframe attribute are not props and nothing is
spread onto the element, so they cannot reach the DOM even through a cast.

*Arbitration (allowlist, not blocklist):* the only tokens a caller may add are
`allow-scripts`, `allow-forms`, `allow-downloads`, `allow-pointer-lock`,
`allow-orientation-lock`, `allow-presentation`. Everything else —
`allow-same-origin`, `allow-top-navigation*`, `allow-popups*`, `allow-modals`,
`allow-storage-access-by-user-activation`, and any token the primitive does not
know — is dropped case-insensitively even if passed; an emptied set falls back
to the default posture (`allow-scripts`), because a frame with **no** `sandbox`
attribute is fully privileged. `loading="lazy"` and
`referrerPolicy="no-referrer"` are not props. The opaque origin IS the
containment: guest content cannot reach the app, its storage, or the preload
bridge.

*Teardown:* it is a plain React element — unmounting your pane/page removes the
frame and its realm; nothing is registered app-side.

Migration for **rss-reader** (#115972): replace the stubbed `/preview` → 501 →
`host.openWorkspace('rss-browser')` → empty `RssBrowserFrame` → `ctx.os.openExternal`
chain with `<SandboxedFrame src={article.url} title={article.title} />` inside
the workspace page; drop the leftover `.rss-browser-frame-host webview` CSS.

### Transcript directives — inline components the model addresses

`TRANSCRIPT_DIRECTIVE_AREA` makes the transcript itself a contribution area.
Register a named directive and the agent can render your component inline in
an assistant message by emitting a paragraph of the form `::name{key="value"}`:

```javascript
import { TRANSCRIPT_DIRECTIVE_AREA } from '@hermes/plugin-sdk'

ctx.register({
  id: 'task-card',
  area: TRANSCRIPT_DIRECTIVE_AREA,
  data: {
    name: 'task', // the model writes ::task{id="BB-12"}
    render: ({ attrs, streaming }) => jsx(TaskCard, { taskId: attrs.id, streaming })
  }
})
```

Rules the host enforces so the surface stays safe:

- The directive must be the **entire paragraph** — `::name` mid-prose stays
  prose, so plugin components can never hijack running text.
- Attributes are **untrusted model output** (`key="value"` pairs, string-only).
  Validate your own fields; render nothing on garbage rather than guessing.
- An **unclaimed** directive (no plugin registered for the name) renders as
  the plain paragraph it always was — nothing breaks when a plugin is off.
- Renders are wrapped in the contribution error boundary: a throw degrades to
  an inline error chip, never a dead message.
- First registration wins on a name collision; namespace adventurous names
  with your slug (`myplugin-board`, not `board`).

Core ships one directive as the reference consumer: `::preview{file="…"}`
renders the workspace HTML file **live inside the message** — a sandboxed
`srcdoc` iframe with an opaque origin (scripts run and the widget is fully
interactive; no reach into the app, its storage, or the bridge). The frame
sizes itself to the content (height live, width adopted from the content's
intrinsic span, flush left in the message flow), and a theme prelude hands
the document the app's resolved tokens (`--foreground`, `--muted-foreground`,
`--accent`, `--border`, `--card`), the app font, and a transparent
background — so widget-shaped HTML reads as native while a full page keeps
its own design. Non-HTML targets and remote gateways fall back to the
classic preview card. Tell the agent about your directive in a skill (that's
how it learns to emit it).

Previewed widgets can also **talk back**. Inside the frame,
`window.hermes.send('get-price eth')` (or a declarative
`<button data-hermes-send="get-price eth">` — no script needed) hands that
prompt to the agent as a user turn, off-screen: no bubble takes up the
transcript, the widget updating is the visible response. The turn is still
real — it wakes the agent, rides the composer's steer/queue rules, and
persists (typed `hidden`) so resume and the session DB keep the full record.
Prompts are trimmed, capped at 500 chars, and throttled to one per second
per frame.

### Mount-scoped chrome (`Contribute`)

`ctx.register` is for **permanent** contributions. When chrome should live and
die with a component that's already on screen (a page's own header control
leaves when the page unmounts), render `<Contribute>` inside it instead:

```javascript
import { Contribute, WORKSPACE_PAGE_HEADER_AREA } from '@hermes/plugin-sdk'

jsx(Contribute, {
  area: WORKSPACE_PAGE_HEADER_AREA,
  id: 'my-page:switcher', // namespace with your slug
  children: jsx(MySwitcher, {})
})
```

It registers on mount and disposes on unmount automatically.

### Sidebar nav visibility and order (`SIDEBAR_NAV_PREFS_AREA`)

A plugin hides or re-orders the sidebar's top nav rows by **contributing a
preference**, not by writing a setting. Core merges every `sidebarNav.prefs`
contribution at render and applies the result to the rows it would otherwise
show; the default list itself never changes.

```ts
import { SIDEBAR_NAV_PREFS_AREA, type SidebarNavPrefsContribution } from '@hermes/plugin-sdk'

// Payload (`data`) of a sidebarNav.prefs contribution
interface SidebarNavPrefsContribution {
  hide?: string[]   // rows to drop
  order?: string[]  // rows to place first, in this order
}

ctx.register({
  id: 'prefs',
  area: SIDEBAR_NAV_PREFS_AREA,
  data: { hide: ['cron'], order: ['capabilities', 'new-session'] } satisfies SidebarNavPrefsContribution
})
```

Nav ids are the rows' own ids. Core rows: `new-session`, `capabilities`,
`messaging`, `artifacts`, `cron` (the `SidebarNavId` type; `artifacts` and
`cron` only render in Advanced mode). A contributed row's id is its
**registered** `SIDEBAR_NAV_AREA` id, which `ctx.register` namespaces to
`${pluginId}:${id}` — a plugin that registered `{ id: 'kanban-nav', area:
SIDEBAR_NAV_AREA }` as `kanban` names that row `'kanban:kanban-nav'` in
`hide`/`order`.

**Arbitration.** Hidden rows are the **union** of every contribution's `hide`
(no plugin can un-hide another's row; hide beats order), except
`capabilities`: the row hosting the Plugins tab is the user's path to a
plugin's own off-switch, so it can be moved but never hidden. Contributions
apply in the registry's area order — **lowest `order`, then registration** —
and the first one's `order` wins: later contributions place only ids not yet
placed, rows no order names keep their default relative order after the
named ones. Unknown ids are inert.

**Teardown.** The contribution lives in the registry, so disabling or reloading
the plugin disposes it and the rows come straight back — nothing to clear.
This is why it is not a `host.sidebar.hide()` verb: `host` is a singleton that
cannot attribute a write, a persisted preference would outlive the plugin, and
two plugins would overwrite each other's order.

**Persisting the user's choice** is the plugin's job, in its own
`ctx.storage`: read the saved prefs on `register`, contribute them, and on every
edit save + dispose + re-contribute (re-registering the same `id` replaces it).

```ts
// sidebar-manager: replaces `[data-sbm-off] { display:none }` + re-parenting <li>s
let dispose = () => {}
const apply = (prefs: SidebarNavPrefsContribution) => {
  dispose()
  dispose = ctx.register({ id: 'prefs', area: SIDEBAR_NAV_PREFS_AREA, data: prefs })
}
apply(ctx.storage.get('navPrefs', {}))
// in the editor's onChange:
ctx.storage.set('navPrefs', next); apply(next)
```

Session sections (Pinned, Recents, Cron jobs) are not covered — nav rows only.

## Host API

Everything on `host` is reachable from anywhere in a plugin. State atoms are
readonly — read with `.get()` in handlers, subscribe with `useValue(atom)` in
components.

```ts
host.state.activeSessionId  // ReadableAtom<string | null>
host.state.awaitingResponse // ReadableAtom<boolean>  true until the first assistant payload
host.state.busy             // ReadableAtom<boolean>  focused chat is working after a send
host.state.busyBySession    // ReadableAtom<Record<string, boolean>>  runtime id → mid-turn
host.state.focusedSessionId // ReadableAtom<string | null>  (runtime id of the FOCUSED session — tile-aware; prefer for session.* RPC)
host.state.focusedSessionProfile // ReadableAtom<string>  (owner profile of the focused chat — prefer over `profile` for per-bot/profile readouts)
host.state.focusedStoredSessionId // ReadableAtom<string | null>  (durable id — navigation / session-list matching)
host.state.focusedUsage     // ReadableAtom<UsageStats | null>  (live streamed usage of the focused session, no RPC needed)
host.state.cwd              // ReadableAtom<string>
host.state.gateway          // ReadableAtom<string>  socket state ('idle' | 'connecting' | 'open' | …)
host.state.model            // ReadableAtom<string>
host.state.profile          // ReadableAtom<string>
host.state.viewport         // ReadableAtom<{ width, height, narrow }>
```

`host.state.gateway` is the WebSocket connection, not whether a chat turn is
running. A session can be mid-turn while the socket is `open`; another session
can be idle at the same time. Disable composer or plugin actions from the
**focused session's** turn-busy (`host.state.busyBySession[sessionId]`, or that
session's `view.$busy`) — never from `gateway`, and never from a process-global
busy flag.

```ts
host.notify({ kind, message, title?, detail?, action? })  // toast; returns id
host.notifyError(error, fallbackMessage)                   // toast an error
ctx.os.notify({ title, body?, silent?, icon?, activate?, onActivate?, actions? })
                                           // native OS notification (attributed to your plugin)
ctx.os.openExternal(url)                   // OS default handler (browser, mail, spotify:) → Promise<boolean>
ctx.os.revealPath(path)                    // reveal in Finder / Explorer → Promise<boolean>
ctx.os.writeClipboard(text)                // system clipboard → Promise<boolean>
host.navigate('/route')                    // hash-route navigation
host.openSession(id, { profile?, intent? }) // open a stored session core-style;
                                           //   profile: soft-swap to that profile's backend first
                                           //   intent: 'in-place' (default) | 'stack' | 'tab' | 'window'
host.newChat(profile?)                     // fresh chat draft, optionally in another profile
host.openWorkspace(id, { render, title?, minWidth?, onClose? })
                                           // dock a plugin-rendered tab into the MAIN
                                           //   workspace zone and reveal it; returns a disposer
host.paneVisibility(paneId)                // ReadableAtom<boolean> — is a contributed pane
                                           //   actually on screen (its zone's active tab)?
host.onEvent(type, fn)                     // gateway event stream ('*' = all); returns disposer.
                                           //   Calls made during register() are retired with the
                                           //   plugin; elsewhere prefer ctx.onEvent (always tracked)
host.logs(...)                             // tail an app log file
host.status()                              // one-shot system status snapshot
host.restartGateway()                      // restart the backend gateway
host.profileRoutes()                       // [{ profile, targetProfile, connectionId, mode }]
host.requestProfile<T>(route, method, params?, timeoutMs?, { spawnPriority? })   // registry-routed RPC; no foreground swap
host.requestProfile<T>(profile, method, params?) // legacy v1/local overload
host.request<T>(method, params?)           // active-gateway JSON-RPC — the real power
host.sessions.pin(storedSessionId, pinned?, index?)  // pin/unpin (default pinned=true); index = slot in Pinned;
                                           //   same store the row's ⇧-click / drop writes
host.sessions.reorder(ids)                 // replace the manual Recents order (what a drag persists); [] resets
host.sessions.reorderPinned(ids)           // permute the Pinned section (the pinned drag path)
host.sessions.setColor(storedSessionId, color | null)  // per-session colour override; null clears
host.skills.list(profile?)                 // every skill for the scope (Capabilities endpoints)
host.skills.setEnabled(name, on, profile?)  // enable/disable a skill — the Capabilities toggle
host.toolsets.list(profile?)               // toolsets + enabled state
host.toolsets.setEnabled(name, on, profile?)// enable/disable a toolset
host.profiles.list(scope?: ProfileScope)   // the profile list the profile rail reads
host.pluginDecisions                       // READ-ONLY atom: this window's plugin on/off decisions (frozen copies)
```

`host.request` is the same JSON-RPC the app itself uses (sessions, config, skills,
cron, kanban, …). `host.requestProfile` accepts a descriptor from
`host.profileRoutes()` and routes that RPC through its exact registry source and
profile without changing the active chat or gateway. The profile-only overload is
retained only for the sole-local/legacy topology; registry-aware plugins should pass
the descriptor so two sources exposing the same profile name cannot collide.

A call that may cold-start a pooled profile backend dials at background priority by
default, and background dials never get the slot the pool keeps free for user actions.
When the call IS a user action (a save, a button press, a dialog opening), pass
`host.requestProfile(route, method, params, undefined, { spawnPriority: 'foreground' })`;
otherwise, with the pool full of warm backends, it waits out the 30-second slot timeout
and fails. Keep the background default for polling and roster warming.

`host.openWorkspace(id, { render, title?, minWidth?, onClose? })` docks a
plugin-rendered view into the **main workspace zone** — the same center area
session tiles and previews use — as a tab, and reveals it. Re-calling it with
the same `id` refreshes the content in place and re-fronts the tab instead of
opening a duplicate. Closing the tab (the tab's Close control or ⌘W) tears the
registration down and fires your `onClose`; the returned disposer closes it
programmatically. Feature-detect it (`typeof host.openWorkspace ===
'function'`) and fall back to a regular contributed pane on older desktop
builds — Bot Mode's group-chat rooms are the reference consumer (main-window
takeover when available, in-panel view otherwise).

`host.paneVisibility(paneId)` returns a readonly reactive atom that is `true`
while a contributed pane is actually on screen: present in the layout tree,
not dismissed or hidden, its zone un-minimized, and holding its zone's active
tab slot (a lone pane in its own zone counts). The id is the
contribution-scoped pane id, `<pluginId>:<paneId>`. Atoms are memoized per id,
so calling it in render is safe. Use it to register companion UI only while
your pane is visible — Bot Mode's Cronjobs pane is the reference consumer: it
registers while the Bots pane holds the sidebar tab and unregisters when the
user tabs back to Sessions. Feature-detect on older desktops
(`typeof host.paneVisibility === 'function'`) and fall back to
always-registered behavior.

`host.profileRoutes()` inventories every registered source in the current connection
registry. Connect-on-demand SSH sources expose a credential-free `default` seed
route without opening a tunnel, so a plugin can be the first caller that dials them;
an SSH `remoteProfile` remains the route's backend `targetProfile`. `connectionId`
is the registry routing identity;
pair it with `profile` for keys and persistence. Endpoint, token, SSH host/key, and
other raw connection fields never cross the plugin IPC boundary. `profile` is the
source-local route used
for requests; `targetProfile` is the backend Hermes profile served by that route.
They differ when a route explicitly maps to another backend profile (for example an
SSH `remoteProfile` override or a legacy per-profile URL alias). This distinction
preserves backend identity without exposing connection secrets.

Profile-shaped plugins get first-class methods too:
`profiles.list` (each profile + its most recent conversation as
`last_session`; pass `include_sessions: false` to skip the per-profile DB
probe; pass `preferred_session_ids: { profileName: sessionId }` for an
exact, existence-checked lookup of one pinned session per profile — each
named row gains a `preferred_session` summary that resolves hidden rows
and compression lineages to their live tip, or `null` when the id is
definitively gone; older gateways ignore the param and omit the field)
and `profiles.create` (`name`, `description`, `clone_from`,
`clone_all`, `no_skills`, `soul`, optional `model` + `provider` pin) — the
ws twins of the dashboard's `/api/profiles` REST routes.
`host.state.busy` is the focused chat's live turn (thinking and streaming).
`host.state.awaitingResponse` stays true from send until the first assistant
payload. Both follow the chat the user is actually looking at — the focused
session tile when one holds focus, else the primary workspace chat (the same
signal the statusbar's busy pulse reads). Subscribe in a component:

```javascript
const busy = useValue(host.state.busy)
```

For token-level detail, listen with `host.onEvent` (`message.start`,
`message.delta`, `message.complete`).

`host.onEvent` streams live gateway events (message deltas,
session lifecycle, tool activity). Listeners are isolated — a throw in your
listener can't affect app dispatch. Every `host` door is async-safe: a sync throw
from an internal helper (e.g. no desktop bridge in a plain browser) becomes a
rejection your `.catch()` sees, never an error-boundary crash.

`ctx.os` is the curated OS door — every way a plugin reaches outside the app
window, in one namespace attributed to your plugin. `ctx.os.notify` posts a
**native OS notification** — the same Electron pipeline the app's own
approval/turn alerts use. It fires only while the user is away from Hermes
(backgrounded / unfocused); use `host.notify` for the in-app toast when
they're looking at the app. Users can silence it per device under Settings ▸
Notifications ▸ "Plugin notifications", and repeats from the same plugin are
throttled, so treat it as a signal for genuinely notable events — not a log.

Rich presentation + activation (extends the original `ctx.os` door):

```ts
ctx.os.notify({
  title: 'New match found',
  body: 'Someone matched your signal',
  icon: '/abs/path/to/icon.png', // Electron Notification icon
  // Body click → focus Hermes + navigate. Same vocabulary as OS deep links:
  activate: 'hermes://index-network/intent/1',
  // or: activate: '/index-network/intent/1'
  // or: activate: { path: '/index-network/intent/1' }
  onActivate: () => focusLocalState('1'), // optional renderer callback
  actions: [
    { id: 'open', label: 'Open', activate: 'hermes://index-network/intent/1' },
    { id: 'dismiss', label: 'Dismiss', onAction: () => dismiss('1') },
  ],
})
```

`activate` is deeplink-compatible: `hermes://index-network/intent/1` and the
hash path `/index-network/intent/1` resolve to the same in-app route (and the
same `hermes://…` URL works as an OS deep link). Action buttons only render on
signed macOS builds; elsewhere the body click still activates. Navigation only
happens on user click — never from a background event alone.

The other doors (`openExternal`, `revealPath`, `writeClipboard`) resolve
`false` instead of throwing when the capability isn't available (older desktop
shell, plain browser) — branch on the result rather than sniffing the bridge.

### Desktop appearance settings — `host.settings`

`host.settings` is the supported door for the small set of Desktop-local
appearance preferences plugins may share with the native Settings page. Every
key is bound to the store atom + setter the Settings page itself uses, so a
plugin write is exactly a user click on that control: it takes effect at once,
persists through the preference's existing storage schema, and the last write
wins (no plugin "owns" the value afterwards, nothing to tear down for `set`).

```ts
type DesktopSettingValues = {
  'backdrop.v1': boolean
  'composerPopout.gesturesEnabled': boolean
  'intro-splash.v1': boolean
  'reasoning.collapsedByDefault': boolean
  sessionListDensity: 'compact' | 'comfortable' | 'detailed'
  tabStripDefault: 'auto' | 'always' | 'never'
}
host.settings.get<K extends DesktopSettingKey>(key: K): DesktopSettingValues[K]
host.settings.set<K extends DesktopSettingKey>(key: K, value: DesktopSettingValues[K]): void
host.settings.subscribe<K extends DesktopSettingKey>(key: K, fn: (value: DesktopSettingValues[K]) => void): () => void
```

```ts
register(ctx) {
  host.settings.set('sessionListDensity', 'detailed')

  // subscribe emits the current value now, then after every native or plugin write.
  const dispose = host.settings.subscribe('backdrop.v1', enabled => { /* … */ })
  // Teardown rule: `host` is a module singleton and cannot tell which plugin
  // subscribed, so YOU retire the listener — otherwise it outlives a disable/reload.
  ctx.onDispose(dispose)
}
```

Arbitration: the allowlist above is closed. An unknown key or a value outside
the key's type throws **synchronously** (`Unsupported desktop setting: …` /
`Invalid value for desktop setting: …`) and nothing is written — `host.settings`
never touches `localStorage` directly, so it cannot bypass a store's schema or
migration. Feature-detect `host.settings` when supporting older Desktop builds.

Deliberately **not** keys, and why:

| Wanted | Use instead | Why not a raw key |
|--------|-------------|-------------------|
| keybind map (`hermes.desktop.keybinds`) | `KEYBINDS_AREA` contribution | a raw map write rebinds every other plugin's shortcuts; the area merges per plugin and is torn down with it |
| active theme / mode record | `THEMES_AREA` (register a theme; the user selects it) | theme selection is per window/profile and arbitrated by the app, not a flat preference |
| `pluginDecisions` (desktop plugin on/off) | the app's Plugins tab (a read-only view is a separate SDK hook) | a plugin toggling another plugin's enable state is plugins interfering with each other |
| `toolView.technical`, `embed-mode`, `titlebarAppActions`, `translucency.v2`, `user-bubble-transparency.v1`, `hermesDesktop.zoom.*` | follow-up keys after each store is audited | some drive the main process or window chrome; each needs its own guard and ownership review before it becomes plugin-writable |

Migration — `hermes-appearance-hub`, which today does
`localStorage.setItem('hermes.desktop.sessionListDensity', id)` followed by
`window.dispatchEvent(new StorageEvent('storage', …))` to wake the app's store
(`readSimpleKey`/`writeSimpleKey`, `readBoolKey`/`writeBoolKey`):

```ts
// before
localStorage.setItem('hermes.desktop.backdrop.v1', String(on))
window.dispatchEvent(new StorageEvent('storage', { key: 'hermes.desktop.backdrop.v1', newValue: String(on) }))
// after — the store notifies its own subscribers; no synthetic StorageEvent
host.settings.set('backdrop.v1', on)
host.settings.set('sessionListDensity', id)          // was hermes.desktop.sessionListDensity
host.settings.set('tabStripDefault', id)             // was hermes.desktop.tabStripDefault
host.settings.set('reasoning.collapsedByDefault', on) // was hermes.desktop.reasoning.collapsedByDefault
host.settings.set('composerPopout.gesturesEnabled', on)
host.settings.set('intro-splash.v1', mode !== 'off') // replaces clicking #setting-field-appearance.intro-splash
```

Reads become `host.settings.get(key)`; its `MutationObserver` on the Settings
page's intro-splash switch becomes `host.settings.subscribe('intro-splash.v1', fn)`
(disposer → `ctx.onDispose`). `prompt-snippets` reads
`localStorage.getItem('hermes.desktop.keybinds')` to back up its shortcut — that
is the keybind-map row above: contribute the default through `KEYBINDS_AREA` and
keep the user's override in `ctx.storage`, not in the app's map.

### Typed capabilities bridge — `host.skills`, `host.toolsets`, `host.profiles`, `host.pluginDecisions`

```ts
type ProfileScope = undefined | null | string | { connectionId?: null | string; profile?: null | string }

host.skills.list(profile?: ProfileScope): Promise<SkillInfo[]>
host.skills.setEnabled(name: string, enabled: boolean, profile?: ProfileScope): Promise<{ ok: boolean; name: string; enabled: boolean }>
host.toolsets.list(profile?: ProfileScope): Promise<ToolsetInfo[]>
host.toolsets.setEnabled(name: string, enabled: boolean, profile?: ProfileScope): Promise<{ ok: boolean; name: string; enabled: boolean }>
host.profiles.list(scope?: ProfileScope): Promise<{ profiles: ProfileInfo[] }>
host.pluginDecisions: ReadableAtom<Record<string, boolean>>   // get() / subscribe() / listen() — no set()
```

These wrap the **same `api/*` module functions the Capabilities page calls**
(`GET /api/skills`, `PUT /api/skills/toggle`, `GET /api/tools/toolsets`,
`PUT /api/tools/toolsets/<name>`, `GET /api/profiles`) with the page's profile
scoping. Omit `profile` to act on the app-wide active profile; pass a name or a
`{ connectionId, profile }` route to configure another profile without swapping
the foreground one. Nothing new is arbitrated: every call is already reachable
through `host.request` — the value is typing plus profile scoping, so stop
calling `window.hermesDesktop.api` raw.

`host.pluginDecisions` mirrors the app's plugin enable/disable map (plugin id →
`true`/`false`; an absent id means the user never chose and the plugin's own
`defaultEnabled` applies). It is **read-only by design**: a `set()` would let one
plugin flip another plugin's enable state — exactly "plugins messing with each
other's functionality" — and `host` is a module singleton that cannot tell which
plugin is calling to restrict a writer to the caller's own id. The object has no
`set` at runtime, not just in the types, and every value it hands out (`get()`,
`.value`, the argument to `subscribe`/`listen` callbacks) is a **frozen copy** —
assigning into it throws instead of leaking into the map the app reads and
persists. Enabling/disabling plugins stays in the
app's Plugins tab; link to it with `host.navigate('/capabilities?tab=plugins')`.

Teardown: the verbs are discrete user-triggered actions that write the same
backend state the page writes, so nothing is owned afterwards and there is
nothing to tear down. A `subscribe()` on `host.pluginDecisions` returns its
disposer — register it with `ctx.onDispose` so a disabled or reloaded plugin
stops listening.

Migration (better-capabilities):

```ts
// before                                                  // after
desktopApi({ path: '/api/skills' })                        host.skills.list()
desktopApi({ path: '/api/skills/toggle', method: 'PUT',    host.skills.setEnabled(name, enabled)
  body: { name, enabled } })
desktopApi({ path: '/api/tools/toolsets' })                host.toolsets.list()
desktopApi({ path: `/api/tools/toolsets/${name}`,          host.toolsets.setEnabled(name, enabled)
  method: 'PUT', body: { enabled } })
desktopApi({ path: '/api/profiles' })                      host.profiles.list()
JSON.parse(localStorage.getItem(                           host.pluginDecisions.get()
  'hermes.desktop.pluginDecisions.v2'))                    ctx.onDispose(host.pluginDecisions.subscribe(fn))
localStorage.setItem('hermes.desktop.pluginDecisions.v2')  // declined — host.navigate('/capabilities?tab=plugins')
row.querySelector('[data-slot="switch"]').click()          // same: the app's Plugins tab owns the toggle
```

## Data layer — React Query + nanostores

Plugins share the app's single `QueryClient`, so plugin queries cache, dedupe,
poll, and invalidate exactly like core screens — never hand-roll a fetch loop.

```javascript
import { useQuery, useMutation, useQueryClient, atom, computed, useValue } from '@hermes/plugin-sdk'

function MyPanel() {
  const { data, isLoading } = useQuery({
    queryKey: ['my-plugin', 'items'],
    queryFn: () => host.request('my.list', {})
  })
  // …
}
```

For state shared between a trigger and its panel (or a poll loop), use `atom` /
`computed` — the same primitive `host.state` uses. Subscribe in the leaf that
renders the value with `useValue`. To invalidate a query from **outside** React
(e.g. a `ctx.socket` frame arriving), import the shared `queryClient`:

```javascript
import { queryClient } from '@hermes/plugin-sdk'

ctx.socket('/events', () => {
  queryClient.invalidateQueries({ queryKey: ['my-plugin', 'items'] })
})
```

## The UI kit and theming

Import the app's real components directly so your UI is native by default:

> `Button`, `Input`, `Textarea`, `Select*`, `Switch`, `Checkbox`,
> `SegmentedControl`, `Tabs*`, `Dialog*`, `ConfirmDialog`, `DropdownMenu*`,
> `ContextMenu*`, `Popover*`, `Tip`/`Tooltip*`, `Badge`, `Kbd`/`KbdGroup`,
> `SearchField`, `ScrollArea`, `Separator`, `Skeleton`, `GlyphSpinner`, `Loader`,
> `EmptyState`, `ErrorState`, `CopyButton`, `StatusDot`, `LogView`, `Codicon`,
> `DecodeText`.

`DecodeText`'s `loop` is opt-in as of this change — it decodes once and holds by default, so pass `loop` explicitly on progress surfaces that should keep scrambling.

Plus helpers: `cn` (class merge), `icons.*` (the app's lucide set), `haptic`,
`profileColor` / `profileColorSoft` (deterministic identity colors), the time
formatters `relativeTime` / `fmtDateTime` / `fmtDayTime` / `coarseElapsed`,
`useI18n` (localized copy — your plugin stays translatable), and
`evaluateRuntimeReadiness`.

**Style with theme variables, never hardcoded colors.** Panes already sit on the
app's editor background — leave the background alone and use vars for everything
else: `var(--ui-text-secondary)`, `var(--ui-text-tertiary)`,
`var(--ui-text-quaternary)`, `var(--ui-stroke-secondary)`, `var(--ui-accent)`.
For canvas drawing, resolve them once with
`getComputedStyle(canvas).getPropertyValue('--ui-accent')`. This is what makes a
plugin reskin automatically with every theme.

## A backend for your plugin

If your plugin needs server-side work, ship a Python `plugin_api.py` and reach it
through `ctx.rest` / `ctx.socket` — a namespace scoped to your plugin **by
construction**.

### One package, both SDKs {#one-package-both-sdks}

A feature that needs a desktop UI **and** agent-side code (a Python plugin, its
backend routes, skills) doesn't have to ship as two co-dependent installs. Put a
`desktop/plugin.js` inside the agent package. When the package lands in any
local `plugins/` root (default home or a profile), the Electron main process
copies that half into `$HERMES_HOME/desktop-plugins/<id>/` beside a
`.hermes-package.json` marker, and the renderer loads it through the exact same
pipeline as the standalone disk door (hot reload included):

```
~/.hermes/plugins/<id>/           # ONE installable folder
├── plugin.yaml                   # the agent half: tools, hooks, commands
├── skills/…
├── dashboard/
│   ├── manifest.json             # { "name": "<id>", "api": "plugin_api.py" }
│   └── plugin_api.py             # backend routes → /api/plugins/<id>/
└── desktop/
    └── plugin.js                 # the desktop half: panes, commands, ctx.rest
```

The `desktop/plugin.js` half is an ordinary disk plugin — same contract, same
imports, same `ctx.rest('/…')` reaching the `plugin_api.py` sitting beside it.
Installing, sharing, or removing the feature is one folder: the app-root copy
is refreshed when the source `plugin.js` changes (`hermes plugins update`, or
**Rescan**) and removed when the package folder disappears. The copy is what
makes the desktop half **app-level**: it exists once, however many profiles
carry the package, and it never appears or disappears when the user switches
the Capabilities profile selector. The renderer never scans `plugins/` itself.
The marker records the package name and its origin (catalog sidecar or git
remote), which is what the **Install here** button on the Plugins page uses to
install the agent half into another profile. The copy is staged beside the
target and renamed into place, so an interrupted copy (a transient file lock, a
crash mid-copy) never leaves a half-written folder behind; a leftover
`desktop-plugins/<id>/` that has no marker and no `plugin.js` is treated as
such damage and replaced on the next **Rescan**, while a marker-less folder
that *does* hold a `plugin.js` is a standalone plugin you installed by hand and
is never overwritten.

Two enable switches still apply, on purpose, and both default to **off**: the
desktop half ships opt-in — it inventories in **Capabilities → Plugins** but stays
disabled until the user toggles it — matching the Python half's
`plugins.enabled` gate in `config.yaml` (the security boundary below). Dropping
a package into `~/.hermes/plugins` is inert on every surface until the user
says otherwise. The desktop half degrades gracefully when the backend half is
off — `ctx.rest` returns errors, not crashes.

:::note
The copy is local to the machine the desktop app runs on. Against a remote
backend, the remote box's `~/.hermes/plugins` is not reachable as a filesystem —
only locally installed packages contribute a desktop half this way. For a
remote backend the install dialog clones the desktop half separately into
`desktop-plugins/`, the same as a desktop-only repo. A package whose agent half
was installed on the remote host without that clone shows its Desktop half as
**unavailable (remote backend)** on the Plugins page — not as a pending copy —
and the tooltip points at **Install from Git** with the Desktop target checked.
:::

### Distributing with an install link {#install-link}

Ship your plugin repo (agent half, desktop half, or both) and link to it with
the `hermes://` scheme — a plain anchor on your website or README:

```html
<a href="hermes://plugin/install?repo=owner/repo&enable=1">Install in Hermes</a>
```

The user gets a confirmation dialog (repo id, source links, a probe of what
the repo ships) and picks components before anything is installed — deep links
never auto-install. `force=1` replaces an existing install; dev builds use
`hermes-dev://`. Full link reference:
[One-click install links](../user-guide/features/plugins.md#one-click-install-links-desktop).

### The Python side

Desktop plugins reuse the dashboard plugin backend mount. Put the backend in a
`dashboard/` subfolder of a regular Hermes plugin and declare it in a
`manifest.json`:

```
~/.hermes/plugins/<id>/
└── dashboard/
    ├── manifest.json      # { "name": "<id>", "api": "plugin_api.py" }
    └── plugin_api.py      # exports `router = APIRouter()`
```

```python
# plugin_api.py
from fastapi import APIRouter

router = APIRouter()

@router.get("/board")
async def board():
    return {"items": ["one", "two", "three"]}

@router.post("/action")
async def action(body: dict):
    return {"ok": True, "received": body}
```

Routes mount under `/api/plugins/<id>/` (`GET /api/plugins/<id>/board`, …).
Backend code runs inside the gateway process, so it can import from the
hermes-agent codebase directly (`hermes_state`, `hermes_cli.config`, …). See
[Extending the Dashboard → Backend API routes](../user-guide/features/extending-the-dashboard.md#backend-api-routes)
for the full backend reference — the mount is identical.

:::caution The Python backend is gated separately
Enabling a plugin in the desktop **Capabilities → Plugins** panel is a renderer-side
choice; it does **not** import Python. A user plugin's `plugin_api.py` is
imported only when the plugin is in the `plugins.enabled` allow-list in
`config.yaml` (and not in `plugins.disabled`). Project plugins (`./.hermes/`)
never auto-import Python. This is a security boundary, not an oversight
(GHSA-mcfc-hp25-cjv7).
:::

#### Pushing events to your desktop half

Your backend runs inside the gateway process, so it can push an update to your
own desktop half over the app's global event stream — the same stream
`host.onEvent` subscribes to:

```python
from hermes_cli.plugin_events import broadcast_plugin_event

broadcast_plugin_event("rss-reader", "feed.updated", {"count": 3})
# → event "plugin.rss-reader.feed.updated" reaches every connected desktop client
```

```javascript
// register(ctx): the subscription is retired with the plugin
host.onEvent('plugin.rss-reader.feed.updated', ({ payload }) => refreshFeeds(payload))
```

`broadcast_plugin_event(plugin_id, event, payload=None)`: the wire name is
always `plugin.<plugin_id>.<event>`. `plugin_id` is your catalog name
(`[a-z0-9_-]{1,64}`, no dots — it is the namespace and can't spell another
plugin's); `event` is the BARE dotted name (`"feed.updated"`, not
`"plugin.rss-reader.feed.updated"`), segments of `[A-Za-z0-9_-]`, so `""`,
`"../x"` or `"a..b"` raise `ValueError` instead of stranding the desktop half
on a name nobody emits. `payload` is a JSON dict (or omitted → `{}`), delivered
as the event's `payload`; the frame carries `session_id: ""` like every global
event. Delivery is fire-and-forget (a wedged client is skipped, never stalling
your handler). Where it lands depends on the process the call runs in:

| Caller runs in | Reaches |
|---|---|
| `hermes serve` (the Desktop backend): `plugin_api.py` routers, plugin slash commands, tools and hooks in the agent turn | every connected Desktop window |
| the `dashboard.turn_isolation` compute-host child (tools/hooks of an isolated turn) | relayed over the host pipe to `hermes serve`, then every window |
| the stdio TUI (`hermes` in a terminal) | that terminal's client |
| `hermes gateway run` (messaging platforms), `hermes chat`, cron, `hermes plugins validate` | nobody — no Desktop client is attached to that process; the call is a logged no-op |

Use this instead of importing `tui_gateway.server` internals; for plugin-scoped frames
with a payload tailored per connection, `ctx.socket('/events')` remains the
richer door.

Migration (rss-reader): drop the `~/.hermes/rss-reader/commands.jsonl` queue,
`GET /commands` and the 3 s `ctx.rest('/commands')` poll — the Python side
calls `broadcast_plugin_event('rss-reader', 'feed.updated', payload)` where it
used to enqueue, and the desktop side replaces the timer with
`host.onEvent('plugin.rss-reader.feed.updated', fn)` inside `register(ctx)`.

### Calling it from the plugin

```javascript
register(ctx) {
  // REST — namespace-relative path.
  const load = () => ctx.rest('/board')                 // GET /api/plugins/<id>/board
  const act  = () => ctx.rest('/action', { method: 'POST', body: { go: true } })

  // Live twin — a WebSocket to your own namespace.
  const stop = ctx.socket('/events', frame => {
    queryClient.invalidateQueries({ queryKey: [ctx.source, 'board'] })
  })
}
```

`ctx.rest` is profile-aware and rejects path traversal (`..`) so you can never
address another plugin's API or a core route through it. `PluginRestOptions` is
`{ method?, body?, upload?: { filename, contentType?, bytes }, timeoutMs? }`.

`ctx.socket` auto-reconnects with backoff until disposed. **It resolves to a no-op
on OAuth remotes** (single-use WS tickets are core-managed) — treat the socket as
an accelerator over polling, never a replacement. Every consumer needs a polling
fallback anyway, since any socket can drop.

For gateway-wide data (not your own namespace), use `host.request` (JSON-RPC) and
`host.onEvent` (the gateway event stream) instead.

## Settings, enable state, and storage

Every plugin — enabled or not — inventories in **Capabilities → Plugins**, where the
user toggles it live (no app restart), reveals its folder, or rescans. The user's
choice is remembered:

- No choice yet → the plugin's own `defaultEnabled` (default `true`). Set
  `defaultEnabled: false` to ship an opt-in plugin that stays dark until the user
  flips it on.
- Explicit choice → persisted and honored across restarts. A disabled plugin
  stays disabled — don't fight it; the user turned you off.

Persist your own state with `ctx.storage`, namespaced to your plugin
(`hermes.plugin.<id>.*`) so plugins can't read or clobber each other:

```javascript
ctx.storage.set('lastTab', 'board')
const tab = ctx.storage.get('lastTab', 'summary')
ctx.storage.remove('lastTab')
```

## Bundled plugins

A plugin can ship in-tree at `apps/desktop/src/plugins/<id>/plugin.tsx` (default
export a `HermesPlugin`). It's discovered by `discoverBundledPlugins()` at boot —
no import, no registry edit — and shares the exact inventory + live
enable/disable contract as a disk plugin. The two differences:

1. It goes through the app's Vite build, so you can write **real JSX** and import
   the SDK by its `@hermes/plugin-sdk` alias.
2. It's still lint-fenced to `@hermes/plugin-sdk` + `react` only — no `@/…` app
   internals.

No desktop plugins ship in the core tree today; the shipped app stays uncluttered
and demos live in the
[`hermes-example-plugins`](https://github.com/NousResearch/hermes-example-plugins)
companion repo.

## Security model

A loaded plugin is evaluated as ESM in the renderer realm with **full app
authority** — the React singleton, the whole SDK (`host.request` gateway RPC,
`ctx.rest`, storage, `navigate`) and the `window.hermesDesktop` native bridge
(files, git, terminal, installs). The isolation the loader provides is **error
isolation only**: a plugin can't crash the app (contributions are error-bounded,
listeners isolated, a throwing `register()` is rolled back and reported on the
plugin's row), but it can do anything the app can. Plugin storage namespaces
are a convention, not a wall.

This is acceptable for **local** sources — a disk file can already run code on
your machine — which is why the disk door only loads local files you (or your
agent) wrote. For [catalog](../user-guide/features/plugin-catalog.md#trust-model)
installs the trust comes from admission — a human reviewed the exact pinned
commit — backed by two tripwires: the `desktop surface` lint at admission and
the loader's import allowlist (`@hermes/plugin-sdk` and `react*` only; a static
or dynamic `import` of anything else, including `https:` URLs, fails the load).
Neither is a sandbox. A future remote-source door will need a real boundary
(iframe/worker + CSP + capability gating) before it can land; do not treat this
pipeline as a trust boundary.

## Pitfalls

- **JSX won't parse in a disk plugin.** The file loads uncompiled — use `jsx()` /
  `jsxs()` (or `React.createElement`), not JSX syntax. (Bundled plugins are built,
  so JSX is fine there.)
- **Only three specifiers resolve:** `@hermes/plugin-sdk`, `react`,
  `react/jsx-runtime`. Any other import surfaces an up-front load error.
- **Never hardcode colors** (`#000`, `black`, `rgb(...)`). Leave the background
  alone; use theme variables (`var(--ui-*)`) for everything.
- **Reference only what you imported.** A component you forgot to import (e.g.
  `StatusDot`) is a `ReferenceError` at render — double-check every identifier in
  your `jsx()` calls appears in the import line.
- **Read state imperatively in handlers** (`$atom.get()`), never from a render
  closure — rapid events will otherwise see stale values. Subscribe (`useValue`)
  only in the leaf that renders the value.
- **Canvas panes must track their container** with a `ResizeObserver` and resize
  the canvas (width/height attributes, not just CSS) — panes resize constantly.
- **Don't poll faster than a few seconds** with `host.request`; prefer
  `host.onEvent` / `ctx.socket` and let React Query dedupe.
- **Bare globals are not tracked.** `window.setInterval`, `window.addEventListener`,
  a `<style>` you append — the host never sees them, so they survive disable and
  every hot-reload (ES modules can't be unloaded; a hot-edit loop stacks live
  copies). Use `ctx.setTimeout` / `ctx.setInterval` / `ctx.addEventListener`, and
  wire anything else to `ctx.onDispose`. Module-scope state is yours to reset.
- **Module evaluation has a 10 s deadline.** A top-level `await` that never
  settles (waiting for a gateway that isn't up) fails the load as `import timed
  out` instead of stalling the plugin scan; do the waiting inside `register()`.
- **One id, one file.** Two folders exporting the same `id` (a standalone install
  beside a unified-package copy) load first-wins in folder-name order; the later
  one shows `duplicate id` on its own row in Capabilities ▸ Plugins.
- **`ctx.socket` is a no-op on OAuth remotes.** Always have a polling fallback.

## Reference

### SDK exports at a glance

| Category | Exports |
|----------|---------|
| Host | `host` (`.state.*`, `.settings`, `.notify`, `.notifyError`, `.navigate`, `.onEvent`, `.logs`, `.status`, `.restartGateway`, `.request`, `.composer`, `.sessions`, `.skills`, `.toolsets`, `.profiles`, `.pluginDecisions`) |
| Plugin contract | `HermesPlugin`, `PluginContext`, `PluginContribution`, `PluginStorage`, `PluginOs`, `PluginRestOptions`, `PluginNativeNotificationInput`, `PluginNotificationAction`, `HermesOpenTarget`, `Contribution` |
| Area constants | `PANES_AREA`, `ROUTES_AREA`, `SIDEBAR_NAV_AREA`, `STATUSBAR_AREAS`, `TITLEBAR_AREAS`, `WORKSPACE_PAGE_HEADER_AREA`, `PALETTE_AREA`, `KEYBINDS_AREA`, `THEMES_AREA`, `COMPOSER_AREAS`, `SESSION_ROW_AREAS`, `SIDEBAR_NAV_PREFS_AREA`, `APPEARANCE_AREAS` |
| Area payloads | `RouteContribution`, `SidebarNavContribution`, `StatusbarItem`, `TitlebarTool`, `PaletteContribution`, `KeybindContribution`, `ComposerMiddleware`, `ComposerAttachmentProvider`, `SessionRowSlotContribution`, `SidebarNavPrefsContribution` |
| React / state | `useValue`, `atom`, `computed`, `useQuery`, `useMutation`, `useQueryClient`, `queryClient`, `Contribute` |
| Theming | `useTheme`, `requestTheme`, `setAccentOverride`, `$accentOverride`, `retintTheme`, `themeHue`, `DesktopTheme`, `DesktopThemeColors`, plus OKLCH math (`hexToOklch`, `oklchToHex`, `oklchToSrgb255`, `mixOklab`, `maxChroma`, `hueDelta`, `normalizeHex`) and sRGB measures (`contrastRatio` — `number | null`, null for unparseable input — `readableOn`) |
| UI kit | `Button`, `Input`, `Textarea`, `Select*`, `Switch`, `Checkbox`, `SegmentedControl`, `Tabs*`, `Dialog*`, `ConfirmDialog`, `DropdownMenu*`, `ContextMenu*`, `Popover*`, `Tip`/`Tooltip*`, `Badge`, `Kbd`/`KbdGroup`, `SearchField`, `ScrollArea`, `Separator`, `Skeleton`, `GlyphSpinner`, `Loader`, `EmptyState`, `ErrorState`, `CopyButton`, `StatusDot`, `LogView`, `Codicon`, `DecodeText`, `SandboxedFrame` |
| Helpers | `cn`, `icons`, `haptic`, `useI18n`, `profileColor`, `profileColorSoft`, `relativeTime`, `fmtDateTime`, `fmtDayTime`, `coarseElapsed`, `evaluateRuntimeReadiness` |

The canonical, always-current export list is `apps/desktop/src/sdk/index.ts`.

### Agents: the `hermes-desktop-plugins` skill

When an agent writes a desktop plugin, it should load the bundled
**`hermes-desktop-plugins`** skill — it carries the same contract as this page in
agent-facing form, with a ready-to-copy `templates/plugin.js`. This page is the
human/developer reference; the skill is the working checklist.

## Troubleshooting

**My plugin doesn't appear.** Confirm the file is at
`$HERMES_HOME/desktop-plugins/<id>/plugin.js` and the folder name matches the
export `id`. Run ⌘K → **Reload desktop plugins**. Check the app for an error
toast naming the failure, and tail `hermes logs gui -f`.

**"unsupported import" on load.** A disk plugin may only import
`@hermes/plugin-sdk`, `react`, and `react/jsx-runtime`. Remove any other import.

**A `jsx` element renders nothing / throws `ReferenceError`.** An identifier used
in a `jsx()` call isn't imported. Add it to the import line.

**`ctx.rest` returns 404.** The backend isn't mounted: confirm
`~/.hermes/plugins/<id>/dashboard/manifest.json` has `"api": "plugin_api.py"`,
that the plugin is in `plugins.enabled` in `config.yaml`, and restart the gateway
(backend routes mount at startup). Tail `~/.hermes/logs/errors.log` for
`Failed to load plugin <id> API routes`.

**`ctx.socket` never fires.** On an OAuth remote it's a no-op by design — use your
polling fallback. Otherwise verify the backend exposes the matching
`@router.websocket(...)` route under its namespace.

**Colors look wrong after a theme switch.** You hardcoded a color. Replace it with
a `var(--ui-*)` theme variable.